In television receivers providing scan up and scan down features, it is well known to include a memory device to store active channel information to enable the receiver to skip over inactive channels and thus increase the tuning speed. It is also known that by the use of a delete key a user can delete marginally active as well as undesired, although active, channels from the list of those to be tuned.
Manual programming of the "skip list" into the memory can be a tedious process due to the large number of channels available in the United States and many other countries. A system employing autoprogramming of the memory is disclosed in U.S. Pat. No. 4,561,112 (Ridder) wherein a scan of available channels is performed automatically and a memory programmed is with active channel data. In this known system, the autoprogramming function is initiated by the user's pressing of keys which generate an "action-start" command.
The memory included within these systems may be volatile or non-volatile. Volatile memory has the disadvantage that a relatively costly standby power supply is necessary for maintaining the active channel data when the receiver is turned off. Non-volatile memory needs no standby power supply, but tends to be more expensive than volatile memory and is, therefore, also not a particularly cost effective solution to the problem of data retention during the periods when the receiver is turned off. Volatile memory becomes more cost effective than non-volatile memory when the standby power supply must be included for another purpose, such as for supplying power to a remote control receiver (which must be continuously powered in order to receive and process an "on" command for the receiver).
A problem arises with the use of standby power to maintain the data in memory because standby power is derived from the AC line and is therefore subject to interruption by AC power failures. Battery backup of the standby power supply for maintaining data stored in memory in consumer electronics devices is not desirable from a safety standpoint since the user would have to come in contact with circuitry connected to circuits within the cabinet to periodically change the batteries. The storage of a charge on a capacitor has been used in known systems to retain the data in memory but typically such systems retain the data only for a relatively short time, e.g., typically from several seconds to several minutes.
Two additional problems are peculiar to "commercial" versions of autoprogramming type receivers, for example, hotel or hospital television receivers. Users of these receivers are typically not familiar with the controls because they are not the owners of the receiver. Therefore, they cannot be expected to be able to, or be inclined to cause the institution's television receiver to be programmed. Also, such commercial versions of receivers may have the controls situated behind a locked door in the cabinet to discourage user readjustment because the non-familiarity of the user with &:he controls may lead to confusion, misadjustment and an unnecessary service call. In an institution operating a large number of receivers using volatile emory for storing skip lists, an AC power failure would cause a loss of programming information in all the receivers at once, necessitating reprogramming of all of them individually by an employee, a costly and time consuming process even if the employee has merely to turn each receiver on and press an autoprogramming key.
U.S. Pat. No. 3,940,702 (Yoshimura) discloses a system which, in addition to allowing autoprogramming anytime at the user's option, automatically reprograms itself every time the receiver is turned on by the user. Since this system reprograms itself each time it is turned on, the data stored in memory need not be preserved. This system has a disadvantage in that a user would quickly become annoyed with a receiver that took the time to scan all available channels every time it was turned on. Also, the list of channels may tend to change too frequently when the automatic reprogramming occurs each time the receiver is turned on considering that the receiver will be turned on at various times of the day and week and the channels may or may not be consistently active. Furthermore, it is quite possible that a user may intentionally delete an otherwise active channel from the memory device as a matter of personal preference. A system which autoprograms the memory device whenever the receiver is turned on would add the deleted channel back to the memory. Thus, the deleted channel will be tuned despite the wishes of the user.